Just back fromt he alternator shop where the guy bench tested it under load and thought it looked great. His thought was that it could be a slipping belt or a bad battery.

I doubt the belt is slipping as I have had to deal with that before. On mine it would squeek soemthing awful on startup until I got it tight enough.

I do wonder though about the battery. When the throttle is applied the voltage immediately goes way down - from ~ 14.5v to ~ 12v. I would think even if I pulled the alternator off line with the vehicle running it should start at 13.8v and then go down a bit at a time.

The battery starts the truck fine but then again the motor is tiny and the compression is low.

I've had GM cars that would start fine but the computer would show a fault with the charging system and the fix was changing the battery.

Any other opinions?

Mark